Bradley Wiggins is at a crossroads in his career following his withdrawal from the Tour de France and urgently needs to set himself new goals, according to Shane Sutton, the Australian who was a major influence on Wiggins up to his Olympic and Tour de France triumphs of last year. "This is definitely a crisis point," said the British Cycling head coach. "What will it do to him mentally? I don't know."

Sutton has known Wiggins since the late 1990s and was a father figure to the Londoner, as well as being his regular drinking partner at one stage. In 2010, after the last crisis in the Olympic gold medallist's career, following his poor form in that year's Tour de France, Sutton was the man Wiggins called upon to put him back on the road. "The only person who knows me and understands me inside out," was Wiggins' description of the Australian.

On Friday Wiggins was ruled out of Team Sky's squad for the Tour de France, because of a knee injury dating back to the Giro d'Italia that, while it has not stopped him riding his bike, has prevented him training at the required intensity, and now requires rest. It is not the first major setback in his career – he went through personal crises in 2010 and in late 2004, following his gold medal at the Athens Olympics. Until recently, he had rarely had to cope with injury, but in late 2012 he suffered a broken rib after a crash involving a van near his Lancashire home, while in July 2011 a collarbone fracture put him out of the Tour.

"When you have a setback like this you need to take inspiration from others, so I'd cite Cadel Evans, who had a rough year last year but has come back to get on the podium of the Giro at 36," said Sutton. "Brad needs to set some goals as soon as possible, something to get him back on his bike. The best would probably be the Vuelta [the Tour of Spain, which starts on 24 August] as preparation for the world championship individual time trial, which is a goal that has eluded him until now."

Sutton believes Wiggins will be hit hard by his withdrawal from the pool of riders Sky will select from for the Tour. "It is a massive setback for him. You can say whatever you want about the Giro, but as the Tour drew nearer he wanted to try for the double."

The Australian has taken a back seat with Wiggins recently, with the physiologist Tim Kerrison – who has been part of Wiggins' backup team since late 2010 – taking the lead role. But Sutton feels that given the intense way in which the 33-year-old worked through 2012, he needs something to refresh his mind.

"He needs to improvise, find some diversity, do different things to get the same result. It's like a sponge washing a car – he's been wrung dry. After last year, from Paris-Nice [in March] to the Olympic Games, the numbers he was hitting were incredible; and it wasn't only that, it was the way he went about it. There was a steeliness there, a toughness, so much appetite.

"Looking back to 2010, we went out and found a new venue for him to train but maybe that has run his course. The other thing to take into account is that he is a family man, with huge responsibilities there; maybe they should be with him more when he's away."

Sutton does not share the view that Team Sky will be stronger in the Tour de France with a sole leader in Chris Froome. "I do know Team Sky will be weaker for the loss of Bradley Wiggins. If both he and Chris Froome are at the race fit and healthy and chafing at the bit, you'd take that, especially with Richie Porte [Sky's young Australian, winner of the Paris-Nice race this year] behind them. So Brad is a massive loss for Sky, but I'm confident it won't be the end of Bradley Wiggins."

Sutton is adamant that Wiggins will bounce back, spurred on by missing the Tour and his setback in the Giro d'Italia. "As far as I'm concerned, he will watch the Tour [on television] and be absolutely sick that he's not there. That could be the spark that lights the blue touch paper. He's 33 but I don't believe he's finished. He just needs something to whet his palate."